1. Field of the Invention
The present invention relates to a data transmission device which is preferably applicable to a sales management system for example a system in which a host computer that is provided in a head office is connected to an electronic cash register provided in each of branch stores through one or more on-line circuits.
2. Description of the Prior Art
In the prior art, there has been used a sales management system, wherein a main store or central processing office having a host unit such as a computer is connected to each of branch stores. The connection is through an on-line circuit so that sales data as an example, transmitted from an electronic cash register provided in each of the branch stores are integrally processed by a host computer provided in the main store or in the central processing office. For example, a unit price of each of the goods and a code of each division (`division` means a minimum sorting category representing goods in the same category having the same price hereinafter) are transmitted from the host computer to the electronic cash register in each of the branch stores. With this structure the performance of sales managements of all the branch stores integrally associated by means of the host computer.
In such a sales management system as described above, in order to sum up the gross sales of all the branch stores in a day, the sales data of each of the branch stores are sent from the electronic cash register in each of the branch stores to the host computer in the main store.
Moreover, in the case that there is provided a main (primary) apparatus which can be a cash register and a plurality of additional (secondary) apparatuses which can be electronic cash registers in each of the branches in such a sales management system, the main electronic cash register can perform a plurality of functions. The functions being for example, performing inspection and liquidation, transferring data sent from the host computer and data set in the main electronic cash register to a plurality of additional electronic cash registers provided in each of the branches, and a function of performing a process of opening and closing the stores.
In the prior art, in the case of transmitting sales data from an electronic cash register provided in each of the branches to the host computer provided in a main store, the data of all the divisions stored in a so called a division file are sent from each of the cash registers to the host computer. In the host computer only the data of the sales division must be retrieved and selected. In such a sales management system, the time for transmitting the data is lengthy resulting in poor transmission efficiency because of the need of useless buffers for the data transmission. Also the processing operation of the host computer becomes complicated in the prior art described.
Moreover, in order to perform the above mentioned functions in the main electronic cash register, an operator skilled in the operation of the main electronic cash register needs to be located in the store where there is provided an additional electronic cash register. Moreover, since the above mentioned functions of the main electronic cash register are performed generally after closing each of the branch stores, an operator of the main register should be located in each of the stores after the closing time of the stores.